Devices for fixing attachments such as adaptors carrying sacrificial wear parts to dragline buckets are known in the prior art.
Generally, the adaptor is fitted onto a corresponding nose portion of the dragline bucket and a spool inserted into a passageway formed through the adaptor and the nose portion. In the past, a wedge was inserted into the passageway between the spool and a tip region of the nose portion and was then hammered into the passageway with a sledge hammer causing the spool to move rearwardly from the tip of the nose portion and press against the adaptor to thereby force the adaptor tightly onto the nose portion.
However, any misalignment in the openings through the adaptor and nose portion forming the passageway, due to wear or improper fitting of the adaptor, caused difficulty when inserting the wedge. Moreover, chips of metal could fly off the wedge or hammer as the wedge was being forced into the passageway posing a safety problem for persons in the immediate area. In addition, a sledge hammer needed to be available in order to insert the wedge, the use of which also posed a safety problem.
A wedging device comprising a wedge connected to a spool by means of a bolt is disclosed in U.S. Pat. No. 4,433,496. The wedge has an arcuate surface which bears against a correspondingly contoured arcuate surface on the spool. When the bolt is rotated the wedge is drawn up the arcuate surface of the spool so that a curved contact surface of the wedge is placed into abutment with the nose portion of the dragline bucket. However, the wedge exerts an offset force against the nose portion causing the adaptor to skew as it is drawn onto the nose portion when the bolt is rotated which presents difficulty to the workperson fixing the adaptor in position
A wedging device consisting of two spools and a separate wedge assembly is disclosed in patent application WO 95/01481. The wedge assembly is comprised of two wedges and a bolt which extends through a passageway formed in one of the wedges and is threadably received in the other wedge. In use, the wedge assembly is positioned between the spools in the passageway formed through the adaptor and the nose portion of the dragline bucket, and the bolt rotated so that the spools are forced apart as the wedges are drawn toward each other causing one of the spools to be pressed against the nose portion and the other spool to be pressed against the adaptor. Accordingly, the movement of the wedges results in the adaptor being drawn onto, and fixed to, the nose portion.
However, the substantial forces which are exerted on the device during an excavating operation can cause a wedge to tilt and so bend the bolt in a region adjacent to the wedge. This may result in difficulty when loosening the bolt to remove the wedging device, and possibly seizure of the device in the dragline bucket. It may also lead to increased downtime of the dragline bucket while the wedging device is removed or at the least, the need for maintenance to the wedging device.
A further wedging device is disclosed in Australian patent application No. 68677/94. This device consists of a single spool and a separate wedge assembly comprising two wedges receiving a bolt. As with the device disclosed in WO 95/01481 the bolt extends through a passageway formed in one of the wedges and is threadably received in the other wedge. Accordingly, the arrangement suffers from the same drawback as the device disclosed in WO 95/01481 in that the bolt is prone to bending forces which may result in damage to the wedging device.
Due to the size of dragline buckets as well as the nature of the forces exerted on the buckets during use, the wedging devices are correspondingly large and typically weigh about 6 kg or more.
As the wedging devices disclosed in WO 95/01481 and AU 68677/94 are comprised of a number of separate unconnected parts, difficulties can arise when fixing the devices in position on a dragline bucket due to the need to align the separate parts with each other. The insertion of the wedging devices may also be hampered if there is misalignment of the adaptor and nose portion of the dragline bucket
The weight of a wedging device of the type disclosed in WO 95/01481 and AU 68677/94 further compounds the difficulty in holding the separate parts of the wedging device together while being lowered into the passageway defined in the nose portion and adaptor. Furthermore, it is common for a workperson to be positioned so as to receive the wedging device from below the passageway as it is lowered into the adaptor and nose portion, and hold the device in position while another workperson tightens the bolt of the wedging device from above the passageway to thereby wedge the separate parts of the device together. The fact that the wedging device exists as separate parts poses safety risks not only to the workperson receiving the device as it is lowered into the passageway but also to the workperson holding the parts together while lowering the device.